Instead, at the agreed time of 5.32pm, the Prime Minister arrived at the dealership - based in his constituency - to purchase a £1,495 blue Nissan Micra for his wife Samantha.

Mr Harris said: "I thought it was one of my mates having a wind-up and I was going to be sat here for half an hour on my own doing nothing - especially when he said it was for a Nissan Micra.

"I thought that 5.32pm was a bit precise, because somebody would say half five, wouldn't they?

"I thought I would play along somehow and stay here until half five, make myself some coffee, do some paperwork, then next thing you know there were two Land Rovers and a Volvo coming round the corner."

Upon meeting the leader of the country, Mr Harris could not resist quipping that it was lucky the car was not red - the colour of the Labour Party.

"Fortunately, it was just the right colour," he said.

Mr Cameron then inspected the vehicle and instructed his aide to stand behind it while he checked the brake lights, staying for about half an hour.

He returned the following day to complete the sale.

Despite the added security, Mr Harris, who has run the car business for seven years, felt it was just a standard transaction.

"It was a bit surreal, but likewise he was just a normal chap buying a car for his wife, a normal conversation, normal sort of deal and that was it," he added.

Asked if he was a supporter of Mr Cameron, the car dealer said: "He seems a nice enough chap."